PLC control cabinet maintenance

Why do you need maintenance?

a, in order to extend the service life;

b, for the stability of equipment operation; if there is a problem in the operation of the equipment, the loss may not stop to maintain this little time,

 

Second, do not maintain easy problems

1, the cabinet will be dirty equipment short circuit, arc, burn equipment;

2, the cabinet fan filter plugged, poor heat dissipation will lead to poor stability of the equipment;

3, humidity assembly equipment short circuit;

4, some high-current location of local overheating time will burn out equipment;

5, other. . .

 

Three preparations

Various tools: screwdrivers, wrenches, shake table, multimeter, clamp ammeter; vacuum cleaners; hot air guns, markers, files and so on;

Spare Parts: Fan Filter, Contact Auxiliary Contacts, Relay Coil, Heat Shrink Tubing, Conductive Paste.

Personnel: Not only electricians but also programmers are required. Because if the programmer involved, the software maintenance done, you can prevent in advance to eliminate many soft faults.

 

Four notes

Do a good job planning, develop detailed steps, step by step. Never believe a shot a head idea, but first consider all aspects of good, take the planning step by step do not do;

Safety first: Disconnect the equipment before disassembling, pay attention to safety;

When cleaning the cabinet, be careful not to get the ash everywhere;

Marked all the moving places, pay attention to observation, such as some of the lines to take over, some of the nose to squeeze over again, you need to observe the equipment in these places after the device is in trouble.

 

Five data backup

First backup procedures, it is necessary, if the day equipment hanging, if there is no procedure, then blind, there is a program at the top for a controller, so for equipment maintenance staff, this is a must;

For data that needs to be archived for a long period of time, such as historical trend curve data for the military industry, you can back up historical trend data to a removable hard disk and then shut down Windows-based operating systems such as the HMI system with wincc intouch;

For some controllers that can not communicate, such as soft starters, you need to manually record the internal parameters to prepare for any eventuality.

 

Six system power

1, the data backup is completed, the implementation of the switch operation, the first disconnect when the power switch off the protection switch; then disconnect the main switch (power on the first control cabinet on the main switch, and then turn on the following protection switch );

2, safety lock, the best security lock after the scene power to prevent accidental transmission.

 

Seven appearance and environmental inspection

Temperature and environmental conditions 0 ~ 40 ℃

Relative humidity below 85%

Amplitude less than 0.5mm (10 ~ 55Hz)

No heavy dust, salt and iron filings

24VDC outlet voltage measurement: is within the normal range

Insulation test system after power off, using shake table test equipment insulation.

 

Eight control cabinet cleaning

Equipment power, the PLC, inverter and other cooling holes with the electronic components shelter, it is best to remove the PLC module.

Only use the vacuum cleaner, can not use compressed air blowing, because the compressed air will blow dust inside the device, and the compressed air often contain water, enter the device will be short-circuited;

After suction check the wiring is loose.

 

Nine cable inspection

1, the big cable is loose: If loose, it is easy to burn out.

2, whether there is a large cable connector black phenomenon: If so, pay attention to check whether the nose line pressure or contact current is too large.

 

Ten equipment ground check

Profibus ground measurement: pay attention to see the shield is aging, shielding aging, bringing ground is not good, easy to cause Profibus site is lost.

Analog signal ground measurement: principle Ibid.

Check whether the ground wire rust, corrosion is handled.

 

Eleven contactor check

Large contactor mounting screws and access to loose

Large contactor contact state: whether the main contact burning traces, check the arc hood is burning black and damaged

Contactor terminal status: whether to burn black

Pull-in time, voltage test: check the contactor's pull-in time, and access to the off-line situation

Contactor pull sound is normal, no noise, how to pull out the "buzzing" sound, then remove the check contact the situation, as shown below:

 

Twelve copper row inspection

Check the heat shrink tube is damaged;

Check the copper connections: If the appearance of the copper is discolored, then the copper may overheat, remove the copper if needed, align it flat, apply the conductive paste and tighten.

 

Thirteen relay inspection

Relay contact state, whether black: After a period of time, the relay contacts may appear gray, the most extreme situation is the auxiliary contacts burn, resulting in the solenoid valve can not be connected or disconnected, as shown below.

Relay coil is loose, if loose, press tight.

 

1, if in the production process appears solenoid valve does not pull or disconnect the case, then follow the steps below check.

Corresponding to the solenoid valve relay LED light is not bright, said that the solenoid valve is energized, no light means no charge;

Use a multimeter to measure relay A1, A2 pins for power.

2, if the solenoid valve in the production process anomalies, you can do the following:

A, in general, will only damage a contact, if the relay has two contacts, a damaged, you can consider the other pair, such as: field wiring for the 11-14 contacts, if damaged, can be replaced by 21 -twenty four. At this point to 11 feet and 14 feet on the line release, change to 21 and 24 feet can be.

B, if the replacement of contacts is not good, you can consider replacing the coil, the important circuit from the selves unimportant removal of the relay can be replaced up, be careful not to insert the wrong direction.

Fourteen replacement filter

According to the scene of the situation, six months or a year to replace the filter;

If the filter is clogged, it will seriously affect the heat dissipation of the device.

 

Fifteen inverter, power regulator fan check

Check the inverter, power regulator fan operation is normal

Check if the vents are clogged and if the fan blows out of the way, it needs to be cleaned.

 

Sixteen equipment fever check

1, the temperature cabinet

2, big cable and bronze temperature

3, cable temperature

    If you have the best imager, if not, you can only take the temperature gun.

 

Regularly check the temperature in the cabinet, the temperature of the large cables and the temperature of the cables in the field to prevent the cables and components from being damaged due to dust accumulation or other reasons.

 

Seventeen pincer ammeter test

General operation of a person, a custody, measurement, hand and live part of the safety distance should be maintained at 10 cm or more.

The first measurement before the estimated load current size is measured, the voltage level, and thus select the range. If you can not estimate, in order to prevent damage to the meter, should choose the maximum range to start measuring, according to the size of the reading to the low-grade switch.

Measuring range is not allowed to replace the range gear. Because the secondary side of the measurement is equivalent to the short-circuit state, switching the gear during the measurement will cause the second momentary open circuit and induce a very high voltage, which may result in the internal breakdown of the clamp ammeter.

In order to reduce the error, the measured wire should be placed in the middle of the clamp meter as far as possible when measuring. When measuring clamp-shaped mouth to be closely integrated, such as noise can be re-opened once, if there is still noise should be carefully checked, if dirt, debris should be eliminated, and then measured.

After the measurement, the range switch should be set to the highest gear to prevent the next time you use the range due to careless failure to select the instrument damage.

Clamp meter is generally used to measure the current distribution transformer low voltage side or motor, it is strictly prohibited to use on the high-voltage lines, so as not to break the insulation electric shock.

 

Eighteen holiday considerations

The main power supply of the equipment can be switched off during the holiday, but the lighting circuit and the fan circuit power are reserved.

Must open the control cabinet ventilation fan or air-conditioning; otherwise rainy days met the equipment inside the resurgence, resulting in short circuit;

Have encountered a Spring Festival, under a few days of rain, the fan did not open; results internal dew condensation within the PLC, voltmeter, ammeter glass drops of water inside the glass, after work to open a hot air gun blew for a long time.

 

Nineteen software maintenance - PLC diagnostic buffer

Equipment hardware alarm recording and finishing:

Equipment problems do not necessarily result in equipment downtime, but they are recorded in the PLC's diagnostic buffer, so checking the record regularly is of great importance to the maintenance of the equipment.

Timely understanding of the site of the problem, find out the reasons for timely preparation.

Some people may say that this stuff do not understand, it does not matter, can be saved as txt file sent to others to help look.

 

Critical diagnostic buffer alarm:

A, a site lost; a while back, this more dangerous, you need to check, such as:

Event 1 of 100: Event ID 16 # 38C4

Distributed I / Os: station return

Address of the affected DP slave: station number: 13

DP master system ID: 1

Log. Base address of the DP slave: Input address: 1020

Log. Base address of the DP master: 1023

Requested OB: Rack failure OB (OB86)

Priority class: 26

External error, Outgoing event

    The more dangerous reasons are: communication may be disturbed or DP bus connector oxidation or shielding layer caused by poor grounding, and now is sometimes lost, for a while back, maybe not when this site is completely lost.

 

B, an analog quantity can not be found, this also needs attention:

Event 2 of 100: Event ID 16 # 2943

I / O access error, writing

P area, word access, Access address: 296

Requested OB: I / O access error OB (OB122)

Priority class: 1

External error, Incoming event

The possible reason is: It is possible that the analogue is disturbed, but the overall problem is not big.

 

C, there is a software problem: similar to the above example B, but this alarm is not able to find a DB block of data, the reason is the software pointer problem, refers to a non-existent address.

    For example, DB80 only 1000 byte, you prepared a pointer addressing procedures, referring to the DBB1000, the error, if only the error does not matter, I'm afraid direct death loop hung up.

 

Twenty Software Maintenance - HMI Alarm

    View equipment alarms, mainly some of the frequently occurring alarms, eliminating the causes of these alarms:

Such as equipment, a flow switch often alarm, you can dismantle clean;